GOVERNORS, FUEL PUMPS AND INJECTION NOZZLES, TYPES, ADJUSTMENTS AND REPAIRS a smooth-running, efficient engine is to be pro duced, the designs of the governor and the fuel pump must be co-ordinated. Indeed, many engine builders have united these two mechanisms into one design. For this reason it is advisable that any discussion of a particular fuel pump should be incor porated into the discussion of its respective governor.
hit-and-miss method of gov erning has been tried out on the low-pressure oil engine, but it has never proved successful. With this arrangement, the scav enging air charge blows into the cylinder on the idle as well as on the power cycles. This results in the removal of a great amount of heat from the hot head, the head generally becoming so cold as to be very irregular in the ignition of the fuel charge. When the fuel charge does ignite, the low temperature of the bulb results in a large heat transfer from the hot gases to the cold bulb. This, of course, lowers the engine's efficiency. There is a still more serious defect. The irregularity of the explosions, and the miss firing when the governor does inject a fuel charge, produces marked "hunting." This destroys the engine's usefulness in any situation where close regulation is demanded.
With the price of gasolene advancing, as it has been doing the past few years, there will be a large field for cheap low-pressure engines of small powers capable of handling distillates. The kerosene or modified gasolene engine will not burn even kerosene in a satisfactory manner where the load is variable. It would seem that the hot-bulb engine must be the type adopted. Since it must be low in cost, the present-day forms of governors cannot be used. The hit-and-miss principle is the logical choice. To accomplish this, probably the hot tube, formerly used on the gasolene engine, will be the ignition device adopted. This re sembles the present day hot-bulb with the exception that the torch is always maintained lighted. The use of a permanent flame would eliminate all the objections mentioned above. On engines above 10 h.p. the advantages of the quantitative governor over the hit-and-miss type make its use advisable even though more costly.
Classes of Governors.—The vast majority of low-pressure oil
engines use a quantitative governor, wherein the amount of fuel injected each cycle is regulated to conform to the power demands.
This may be accomplished by either of two means. By the first method the stroke'of the pump plunger is regulated, thereby delivering a varying quantity of oil to the nozzle. The second method consists of some arrangement whereby the opening of the pump suction valve, or of a by-pass valve, limits the fuel en tering the cylinder to the amount actually required to carry the load. Both in effect might be compared to the automatic cut-off governor so popular with high-speed steam engine builders.
While a few builders employ.fly-ball governors similar to those used on throttling steam engines, the majority have adopted shaft governors of either the centrifugal or inertia type. The use of the shaft governor allows the eccentric to act directly on the pump mechanism, and this type is more favorably received by operating engineers.
Muncie Oil Engine Co.'s Governor.—The form of governor shown in Fig. 288 is used extensively certain modifica tions. This particular governor is that used on the Muncie oil engine. It consists of two weighted arms pivoted at A to a disk B that is keyed to the crankshaft.. The extensions of these arms are pivoted at the points C to the eccentric plate which is held in guides that are a part of the disk B. The disk B has slots in it to allow the lever pivots at C to project through into the eccentric plate. As the engine comes up to speed, the arms tend to move outward, this movement being resisted by the ten sion springs. If the load on the engine is decreased, the engine speeds up and the weights overcome the spring tension and move outward, due to the increased centrifugal effect. This move ment of the arms continues until the increased spring tension equalizes the centrifugal force due to the increased sliced. The movement of the arms causes the eccentric to slide in the guides and, consequently, alters the stroke of the fuel pump. If the speed decreases, the movement of the arms and eccentric is, of course, the reversal of the above, resulting in the pump stroke 13ngthening.